1). Field of the Invention
This invention relates generally to a semiconductor processing system and, more specifically, to the semiconductor processing system which allows for processing on opposing faces of a wafer.
2). Discussion of Related Art
The manufacture of integrated circuits involves subjecting a semiconductor wafer to respective processing steps. Any one of a number of processing steps may be carried out including deposition of a layer of material onto the wafer, etching a layer of material which is formed on the wafer, or causing chemical reactions with material formed on the wafer.
Each of these processing steps is carried out in a respective semiconductor processing chamber. One or more of these processing steps may be carried out in a chemical vapor deposition processing chamber such as the processing chamber 1 shown in FIG. 1A. A wafer 2 is inserted through an opening (not shown) into the processing chamber 1 and located on a susceptor 3. Upper heat lamps 4 are generally used to radiate infrared light through an upper window 5 of the processing chamber 1 onto the wafer 2. Lower heat lamps 6 may also be used to radiate infrared light through a lower window 7 of the processing chamber 1 onto the susceptor 3. By controlling power supplied to the heat lamps 4 and 6 the wafer 2 can be maintained at a required processing temperature.
One or more gasses are then introduced into the processing chamber 1. These gasses then carry out one of the processing steps, as previously discussed with the wafer 2 being maintained at a required processing temperature.
In some instances, it may be desirable to process a wafer on opposing faces thereof. FIG. 1B illustrates the apparatus shown in FIG. 1A which is modified for purposes of processing on opposing faces of a wafer. The wafer 2 is elevated from the susceptor 3 by means of a lifting assembly 8a having one or more seats 8b which make contact with a lower face of the wafer 2. With the wafer elevated above the susceptor, processing gasses are permitted to flow through a passage 9 between the wafer 2 and the susceptor 3. By spacing the wafer 1 a distance from the susceptor 3 it becomes more difficult to control the temperature of the wafer 2 via the susceptor 3. In addition, the process gasses tend to flow faster over the upper face of the wafer than through the passage 9 defined between the lower face of the wafer 2 and the susceptor 3, with resulting differences, or lack of control, of processing rates on the upper and lower faces of the wafer.